Gasoline engines are typically designed so that under full load (open throttle) no uncontrolled combustion (knocking) occurs which limits the combustion ratio. Under throttled conditions, the gasoline engine is under compressed which can reduce engine efficiency. Diesel engines are typically over compressed to enhance starting in cold conditions. Diesel engines that have warmed up would be more efficient if they had a lower compression ratio. Thus, a variable compression ratio engine can be operated under various operating conditions to vary the engine compression so as to, for example, increase engine efficiency. A need exists for an improved variable compression ratio engine and related methods.